Tool for forming polygonal sides upon a hollow metal shell.



W. E. SHERBONDY.

TOOL FOR FORMING POLYGONAL SIDES UPON A HOLLOW METAL SHELL.

APPLICATION FILED AUG-7. 1914-,

Patented Sept. 7', 1915.

WITNESSES x'rnnr oFrroE.

WILLIAM E. SI-IERBONDY, OFCLEVELAND, OHIO, ASSIGNOE, BY ME SNE ASSIGNMENTS, TO THE BIGSBY ROTARY MANUFACTURING COMPANY, OF CLEVELAND, OHIO, A

CORPORATION OF OHIO.

TOOL FOR FORMING POLYGONAL SIDES UPON A HOLLOW METAL SHELL.

Application filed August 7, 1914 Serial No. 855,602. 7

To all whom it may concern I Be it known that I, WILLIAM E. SHER- BoNDY, acitizen of the United States, and resident of Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in Tools for Forming Polygonal Sides Upon a Hollow Metal Shell, of which I hereby declare the following to be a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

The objects of the invention are to provide a tool or tools for forming the sides and angles upon a polygonal hollow blank formed of thick sheet metal exemplified as used for forming thesides and angles upon the hex agonal portion of the shell of a spark plug.

The difficulties encountered in forming the shell of a spark plug from sheet metal are very great on account of the thickness of the walls of the shell required since it must be thick enough to receive the external screw thread upon the lower portion and the internal screw thread and external projecting angles of the hexagon upon the upper portion. The diameter of the shell is also so small that it greatly increases the'difliculties involved in the operation.

The invention is illustrated inthe accompanying drawings, hereinafter more fully described, and specifically pointed out'in the claims.

In the accompanying drawings Figure 1 is a perspective view of the blank from which the hexagonal shell is formed; Fig. 2 is a vertical section of the punch and die which perform the preliminary step toward forming the hexagonal portion of the shell; Fig. 3 is a plan View of the die, shown in Fig. 1 and showing the manner of drawing out the corners of the hexagon; Fig. 4 is a similar section to Fig. 2, showing a more advanced step in the process, the angles being nearly formed; Fig. 5 is a plan view of the die; Fig. 6 is a section showing a punch and die which draw the corners into a close approximation of the final shape; Fig. is a plan view thereof, and Fig. 8 is a sectional view of closed compressing dies which give Specification of Letters Patent.

a perfect finish to the corners and surfaces of the blank.

In these views A is a hollow cylindrical blank formed from sheet metal and having a reduced lower portion a. The portion of larger diameter A is larger in diameter than the diameter of the hexagonal portion of the shell of the spark plug to be formed from it for the reasons hereinafter set forth. The blank is capped at the lower end and after the sides and angles have been perfectly shaped as much of the cupped end can be removed as may be necessary to provide an opening through which the electrode projects. a

B is a die having a hexagonal opening B, the angles of which project radially beyond the sides at 6,- Z), and the upper corners of the opening are rounded with a smooth flowing curve, which is preferably composite as at b, 7), to exert a gradual pressure upon the sides of the upper portion of the blank to reduce its diameter and to gradually draw out the angles on the sides.

C is a punch which is formed with portions of two diameters. The upper portion 0 having substantially the diameter of the inner surface of the upper portion of the shell of the spark plug and is a fixed dimension which does not change during subsequent operations upon the shell. The lower portion of the punch substantially fits the inner surface of the lower portion of the blank.

In Figs. 1 and 2 the upper portion of the blank is shown much larger than the upper portion of the punch and is gradually drawn in to meet the punch, while the corners are gradually pressed out to fill the extended angles of the die.

The shoulder within the blank is formed by the lateral pressure of the curved sides of the die as the punch descends and the smooth curvature of the corners of the die prevent the lower portion of the blank from breaking away from the upper portion thereof as the metal is being drawn out- Modifications of this die and punch are shown in Figs. 4, 5, 6, and 7, where the lower end of the punch is gradually reduced in diameter and elongated to elongate and reduce the lower end of the blank until the final size of the shell is closely approximated. The projecting radial angles of the die are also gradually reduced to shorten the corners and perfect-the angles. One or two sets of dies and punches may accomplish the desired results, or with some metals or harder metals a greater number of dies may be required before a perfect shape is ob tained.

If desired the closed dies D and punch P shown in Fig. 8 may be employed to put a final finish upon the blank. Here the punch is provided with portions C and 0 having the exact shape of the interior surfaces of the shell, and also with a shoulder D which compresses the outer edge into perfect shape. The die corresponds to the finished outer surfaces. Spring actuated stripping devices are lalso employed as shown at O, O, and P, T.

Having described the invention what I claim as new and desire to secure by Letters Patent is:

1. In a tool for forming polygonal sides upon a cup shaped blank having portions of two diameters andvhaving its upper portion of larger diameter than the required diameter of the finished product, comprising a die having a polygonal opening, the angles of said opening tapered and radially extended and the upper edge of said opening and its extensions formed in a smooth flowing curve, and a punch having portions of two diameters, separated by a shoulder, the upper portion of the punch having the diameter of the finished product, and the lower portion reduced therefrom and having a rounded extremity.

2. A tool for forming hexagonal faces and corresponding angles upon a cup shaped blank having portions of two diameters, a die of larger diameter than the larger portion of the blank and having a hexagonal opening, the angles in said opening extended radially and tapered to an edge, and a punch having portions of two diameters separated by a shoulder, the upper portion of the punch having the internal diameter of the finished product and less than the internal diameter of the upper portion of the cup shaped blank.

- 3. In a tool for forming hexagonal sides upon the body portion of a cup shaped blank having a body and a reduced inner end, a die block having an opening provided with hexagonal sides, and outwardly curved upper edges, and a punch having a reduced portion fitting the opening in the reduced inner end of the cup shaped blank, said punch also having a body portion of less diameter than the internal diameter of the body of. said blank, the angles of the opening in said die having tapered extensions providing means for the outward flow of metal, at said corners.

In testimony whereof, I hereunto set my hand this 24th day of July, 1914.

' WILLIAM E. SHERBONDY.

In presence of RALPH WV. JEREMIAH, WM. M. MONROE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

